The present invention relates generally to quick-change tooling for metal-working operations, such as boring and turning, and more particularly to a method and apparatus for adjusting the center-height of the cutting tool.
A quick-change tool holder typically includes two separate components--a tool support member and a cutting head. The tool support member is installed on the machine and the cutting head clamps to the support member. The tool support member will normally receive many different types of cutting heads which can be interchanged with one another relatively quickly. Thus, quick-change tooling greatly reduces set-up time when switching from one machine operation to another.
The drawback with quick-change tooling, however, is that it is more difficult to maintain proper center-height adjustment of the cutting tool. Quick-change tooling requires a greater number of parts than conventional fixed tooling. Even when the parts are manufactured according to close tolerances, the cumulative effect of such tolerances can have a significant effect on center-height adjustment. Improper center-height adjustment may result in increased cutting forces in the tool which could significantly affect tool life. Other problems associated with improper center-height adjustment include excessive chatter during machining operations, rough surface finish on the workpiece, and unacceptable variations in the size of the finished workpiece.
In our co-pending application filed contemporaneously with this application, a mechanism is disclosed for adjusting the center-height of the cutting tool in a quick-change tool holder assembly. Briefly, the clamping mechanism includes a key which engages a corresponding keyway in the shank of the cutting unit to angularly locate the cutting unit. The clamping mechanism is mounted in the axial bore of the support member and means are provided for rotating the clamping mechanism. Since the center-height of the cutting tool is dependent on the angular location of the cutting unit, rotation of the clamping mechanism provides a convenient method for adjusting center-height of the cutting tool.
The above-described system is more than adequate in all but the most demanding applications. However, the adjustment mechanism does not assure exact, center-height repeatability. By necessity, there must be some clearance between the key on the clamping mechanism and the keyway on the cutting unit. Each time the cutting unit is clamped to the support member, a different side of the key could possibly engage with the adjacent side of the keyway. Further, it is possible that the clamping mechanism itself could locate the cutting unit such that the key does not engage either side of the keyway. As a result, exact location of the cutting head cannot be assured.
Accordingly, there is a need for a center-height adjustment mechanism in which exact angular location of the cutting unit can be obtained to assure center-height repeatability.